Defence lawyers for the doctor charged over Michael Jackson’s death are seeking urgent testing of two syringes and an IV bag found in the singer’s mansion.

Arguing that evidence was deteriorating, lawyers for Conrad Murray said during a 40-minute closed session with a judge that liquids in one of the syringes had already dried up and was now “salt”, according to a transcript of the proceeding obtained by The Associated Press.

Quantities of substances in the syringes and IV bag could be crucial to explaining how the singer died, the lawyers told the hearing.

Dr Murray has pleaded not guil-ty to involuntary manslaughter. Authorities say he administered a lethal dose of sedatives, including the anaesthetic propofol, to Michael Jackson, 50, in the bedroom of his rented mansion in June 2009.

Officials tested what was in the items and found traces of propofol and lidocaine, according to the transcript. But the amounts of the substances were not determined and defence lawyers say that may be significant in the case expected to hinge on technical and scientific data.

Superior Court judge Michael Pastor declined to order testing on the substances on Tuesday because he wanted defence lawyers to confer further with prosecutors.

The judge might order the testing late next week if the two sides can agree on how it will be conducted.

“I want to act as quickly as we can,” Judge Pastor told the lawyers.

But defence lawyer Ed Chernoff struck an urgent tone, telling the judge: “We are doing it because the house is on fire. We need a hose.”

Mr Chernoff said substances in one broken syringe found at the mansion had dried up since June 2009, when Judge Pastor ordered the evidence preserved. The tests sought by Dr Murray’s lawyers will destroy the samples and can only be performed once.

Prosecutor David Walgren questioned why defence lawyers had not raised the issue sooner.

“There are very technical, complex issues,” he told the judge, adding he thought an agreement on the testing could eventually be reached.

Defence lawyer Michael Flanagan told the judge his efforts to get the substances tested had been delayed because an expert in the Los Angeles County coroner’s office had been on a long holiday. He said the tests should have been done after Jackson’s death.